Some carb ?'s

wiredgeorge wrote:

Your manual is wrong. 26 pumpers were used in the first part of 79 and only on the LTD model then they switched to 28 pumpers as are on all the other KZ1000s. The carbs pictured are VM28SS w/accelerator pump. They should measure 28.7mm ID on the engine side venturi.

Well, there ya go...

Thanks for the info. Guess I'm missing a supplement for that pdf manual I bought off ebay. The Clymer isn't much help on the carbs either. I'll just keep looking for an original factory manual to augment my amateur mechanic skills.

Thanks again,
Sonny

There is little, if any info on the VM26 pumper carbs. The info that is out there is pretty lame as far as tuning. They want you to totally close the mixture screws (on bottom near bowl). The 26 pumper carbs are tough to tune and tough to rejet if any airbox/pipe changes are made. I don't like them. The 28s are far easier to tune. Unlike the 28s, the 26s have an additional diaphragm for the air cut off valve under the pump diaphragm.

wiredgeorge wrote:

There is little, if any info on the VM26 pumper carbs. The info that is out there is pretty lame as far as tuning. They want you to totally close the mixture screws (on bottom near bowl). The 26 pumper carbs are tough to tune and tough to rejet if any airbox/pipe changes are made. I don't like them. The 28s are far easier to tune. Unlike the 28s, the 26s have an additional diaphragm for the air cut off valve under the pump diaphragm.

Well, now that I know, by your observation and my measurement, that I have the 28's, can you provide me with an answer to my original question of what jet size, in your opinion, would be the most appropriate for the combination of stock engine, stock airbox w/K&N, and Kerker 4-1?

As I said before, there are 115's in there now and the plugs always seemed a bit too dark in my opinion. I have a set of 112.5's and 110's on the way and the rebuild kit has 102.5's and 105's.

Maybe I'm just being naive in thinking that I could nail the jetting on the first try.

Sonny

I'm no help on carbs, but after a little research to help identify 1979-80 pumper carbs. Dual fuel inlet only used on the LTD, the A,E and Z1R used single fuel inlet. 26mm LTD in 1979 used pilot screw adjust carbs, where 1980 used air screws with tamper resistant caps on them. So if you have dual inlet, with air screws they are 28s, dual inlet with pilot screws are 26mm

RonKZ650 wrote:

I'm no help on carbs, but after a little research to help identify 1979-80 pumper carbs. Dual fuel inlet only used on the LTD, the A,E and Z1R used single fuel inlet. 26mm LTD in 1979 used pilot screw adjust carbs, where 1980 used air screws with tamper resistant caps on them. So if you have dual inlet, with air screws they are 28s, dual inlet with pilot screws are 26mm

Yep, 28's, that's what I have.

Funny, the rebuild kit I have includes the "tamper resistant caps" for the air screws...like I'm going to hammer those things back in...:laugh:

Sonny

There were two different air screws used. The caps were used on the ones that are sunk way down deep. The other air screw head sits about flush with the well it screws into and no cap could be used.

OK... those carbs you are using came pretty lean. 5CN29 jet needles with O-4 needle jet. 102.5 main and 15 pilot with 2.0 slide cut out. Hopefully, the accelerator pump is working otherwise the jetting tips I mention will be incorrect.

You have checked the accelerator pump, haven't you?

Since you can't do much with the jet needles (no adjustment slots), try the 110 mains and leave the 15 pilots in place. Also check your coil voltages as the dark plugs may not be due to the carb jetting. We have a coil repowering how-to on our website under wg's Tech Stuff Index.

wiredgeorge wrote:

You have checked the accelerator pump, haven't you?

Yep, when I first took them off it squirted in all but carb #4. Hopefully my cleaning has cured that plus, I have a rebuild kit coming for the pump also. Even though it worked, the diaphram looks to have seen better days.

Since you can't do much with the jet needles (no adjustment slots), try the 110 mains and leave the 15 pilots in place. Also check your coil voltages as the dark plugs may not be due to the carb jetting. We have a coil repowering how-to on our website under wg's Tech Stuff Index.

As earlier stated, the spark looks good and I have battery voltage at the coils. I have seen the repowering mod and am prepared to do it if needed in the future.

Thanks for taking the time to reply!I'll give that a try.

Sonny